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A Numerical Approach for Space Charge Limited Bipolar Flow in Cylindrical diodes
oleh: Mei Yan Liao, Ruo He Yao, Ying Bin Zhu
Format: | Article |
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Diterbitkan: | IEEE 2021-01-01 |
Deskripsi
In this paper, a numerical iteration approach to resolve the space charge limited (SCL) bipolar flow problem in cylindrical geometries has been developed. Such an approach is basis for the simultaneous determination of the unknown current densities and the potential distribution. We employed this method to study the characteristics of the SCL bipolar flow. By considering a cylindrical geometry with a cathode radius <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ c}}$ </tex-math></inline-formula> and an anode radius <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ a}}$ </tex-math></inline-formula>, the enhancement over the classical Langmuir-Blodgett (LB) law is investigated as a function of <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ c}}/R_{\mathrm{ a}}$ </tex-math></inline-formula>. It is found that for the bipolar flow model, the SCL current density can be given by <inline-formula> <tex-math notation="LaTeX">$F\mathbf {\times }J_{\mathrm{ LB}}$ </tex-math></inline-formula>, where F and <inline-formula> <tex-math notation="LaTeX">$J_{\mathrm{ LB}}$ </tex-math></inline-formula> represent the enhancement factor on account of the influence of ions and the LB law, respectively. The enhancement factor F follows a <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ c}}/R_{\mathrm{ a}}$ </tex-math></inline-formula> scaling and gradually converges to a constant with increasing <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ c}}/R_{\mathrm{ a}}$ </tex-math></inline-formula>. The planar bipolar flow solution is recovered in the condition where the values of <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ c}}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$R_{\mathrm{ a}}$ </tex-math></inline-formula> are much greater than that of the gap spacing.